By all accounts, he was a sweet child. There were no signs — like in the movie, “The Omen” — that Nicholas Lou “Nick” Saban had a devilishly demanding side.

He was a good son. Starting at age 11, he helped his father run the family roadside gas station deep in the heart of West Virginia’s coal country.

Despite his size (5-foot-8, 185 pounds), the hard-hitting Saban got a football scholarship to Kent State and a way out of Fairmont, W.Va.

He went into coaching, and this is where the changeling began. He could change young men with his steely-eyed stare or his demanding, meticulous nature or his sheer will.

“He sets clear expectations,’’ Alabama center Barrett Jones told The Post. “If you follow them, everything will be fine. If you don’t, he has no problem dismissing you from the organization.’’

Saban, in pursuit of his fourth BCS National Championship with the Crimson Tide, turned 61 on Wednesday.

He has the energy of a man half his age. He works through lunch, always eating an iceberg lettuce salad topped with cherry tomatoes, sliced turkey and fat-free Dijon mustard dressing.

His star tight end, Michael Williams, said at SEC media day he has never seen Saban yawn.

Of course not. Humans yawn. Saban prepares.

He prepares to prepare. He prepares in ways other coaches haven’t even considered preparing.

That preparation was never more on display than in last season’s BCS National Championship game when his Alabama team avenged a 9-6 regular-season loss to LSU with a 21-0 domination of the Tigers.

The two SEC superpowers meet again tonight in Baton Rouge with a spot in the national championship game very much on the line.

The Tide (8-0, 5-0 SEC) have won 11 straight — the longest streak in the nation — since that LSU loss. The Tigers (7-1, 3-1) suffered a surprising loss at Florida and can’t afford another.

All of the pressure should be on Alabama. The Tide are ranked No. 1. The Tide are on the road. The Tide are nine-point favorites, a staggering number in considering LSU’s recent strength.

But Saban is the great equalizer, the goblin other college coaches can’t shake.

He has psychological profiles of every player on his roster. He has brought in professional actors to lead players in improv training geared toward improving communication.

He brought in experts from Pacific Institute, a leadership-development company, to work on their mental toughness.

“One hour a week we work on controlling our thoughts,’’ Jones said. “I know in games I’ve learned how to shut out crowd noise.’’

“Do you mean to say,” I asked, ‘that you won’t hear any of the 92,452 screaming Cajuns tonight in Death Valley?”

“Lock in,’’ Jones said, “lock out.’’

The Tide have been especially locked in this week. Saban found a flaw in his preparation before last season’s donnybrook with LSU.

“If there was anything that I would say about last year’s game, it is I think there is such a thing as being too ramped-up for a game,’’ Saban said. “Everybody has a place and a recipe and a formula for how they play their best. That is obviously the goal for every week that you play.

“Now, when you play in games like this everyone would say that it is really critical that you play your best in a game like this. The formula and the recipe for that doesn’t really change. Even though you would like to change it and put some more sugar in the cake to make it taste better, it usually makes it taste worse.’’

This is as flowery as Saban gets. Usually it’s iceberg lettuce, the Chevrolet of lettuces. But just remember, Saban’s spirit is always at work, thinking of an edge, finding an opponent’s weakness, chasing perfect preparation.